The present invention generally relates to electrical actuators, and more specifically to isolating electronics used for actuators for industrial applications such as for an engine or a turbine.
Electrical actuators are commonly used in industry applications for implementing control over engine or turbine parameters. For example, electrical actuators may be used to position a butterfly valve that controls fluid flow through a turbine. One significant environmental consideration in such industrial applications is that turbines and engines produce a significant amount of vibration during operation. Because electrical actuators are typically mounted directly to the turbine or engine via mating flanges or brackets, vibrations are transmitted from the engine or turbine directly to the electrical actuator. However, it is desirable not to subject the electronics for controlling electrical actuators to such engine or turbine induced vibrations as such vibrations can cause failures or reliability problems in the electronics thus shortening the lifespan.
One prior art attempt of dealing with this problem has been to mount the electronics at a remote location isolated from the vibrations. However, this is undesirable for the customer as two separate assemblies must be separately mounted, proper wiring and electrical connections of the separate assemblies is required, and valuable space is used. For these and other reasons, it is desirable to incorporate the electronics integrally into the electrical actuator. Such desires to have integral electronics are not easily reconciled with the environmental difficulties associated with vibrations. Such engine or turbine induced vibrations have a potential detrimental effect on actuator electronics. A desire thus exists for a solution to this problem.
The present invention is directed toward a rotary electrical actuator for mounting to a support surface in industrial applications having integral electronics that are isolated by vibration isolators from vibrations. The rotary actuator according to the invention comprises a stator housing supporting a lamination stack and coils. The actuator housing has a mounting structure for mounting to the support surface (such as the mounting surface of an engine or a turbine for example) for support thereby. A rotor is carried for rotation in the stator housing. The actuator further comprises an electronics housing containing the electronics that control output of the electrical actuator. Vibration isolators supported by the stator housing in turn support the electronics housing, whereby vibrations received at mounting structure and traveling through the stator housing are dampened prior to traveling to the electronics housing.
It is an aspect of the invention that the vibration isolators comprise a plurality of tie rod assemblies. The tie rod assemblies are inserted into pairs of axially opposed holes in the electronics housing and stator housing. Each tie rod assembly has a first end supported by the stator housing and a second end urging the electronics housing toward the stator housing. Each tie rod assembly includes a threaded fastener at one end thereof fastening each tie rod assembly together to urge the electronics housing toward the stator housing. A stop mechanism limits the fastening of the threaded fastener by engaging an axially aligned stop surface on the threaded fastener. This provides a barrier gap between the electronics housing and the stator housing thereby preventing direct transfer of vibrations. The axially aligned stop surface projects radially outwardly relative to the threads of the threaded fastener to maintain this barrier gap. To dampen vibrations, at least one resilient member is used to dampen vibrations. The resilient member is supported by the stator housing, engages the tie rod assembly and supports the electronics housing.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.